The present invention concerns a universal wrench for tightening and loosening polygonal assembly elements, such as nuts, bolt heads or polygonal tube sleeves.
Universal wrenches provided with gripping mechanisms with adjustable rigid jaws such as adjustable or rack spanners are already known. These wrenches or spanners require a large clearance around the assembly element which has to be gripped. In this case, the gripping of the assembly element is essentially effected laterally in order to hold it securely.
Strap or band wrenches which allow objects of large diameter to be tightened and loosened are also known. This type of wrench is typically for dismantling tubular assemblies, automobile vehicle filters or receptacle caps for example. In this case, gripping is effected by the friction of the strap on the surface of the assembly element. The strap thus preferably has a high friction coefficient in order to transmit the necessary tightening or loosening torque. As will easily be understood, the torque transmitted by friction by means of this type of wrench can thus be reduced by any grease, oil or dirt present which has the effect of reducing the friction between the contact surfaces of the assembly element and the strap. This reduction is all the more probable given that the wrenches are typically inserted or used in environments where such grease, oil or dirt are highly likely to be present.
The diameter of the assembly element also plays an important role since the torque transmitted is directly dependent on said diameter. For a given torque, the force to be applied to the assembly element is in fact inversely proportional to the diameter of the assembly element. By way of example, to transmit a torque of 5 Nm to an assembly element with a diameter of 10 mm the effort applied will be 1000 N. It will thus be understood that if such wrenches are perfectly suitable for applications for demounting filters or tubular assemblies, this is not however the case if one attempts to use this type of wrench for tightening or loosening assembly elements of smaller diameter such as bolt heads or nuts.
Associated with any presence of grease or oil or other friction reducing substances, the small diameter of the assembly elements makes this type of wrench practically unusable for tightening or loosening bolt heads, nuts or other similar polygonal assembly elements.
Another difficulty related to gripping assembly elements such as bolt heads or nuts lies in the small space available in height for gripping to be performed.
The main object of the present invention is thus to provide a universal wrench particularly suited to tightening or loosening polygonal assembly elements such as nuts, bolt heads or polygonal tube sleeves.
Another object of the present invention is also to assure an adequate and optimum grip of the wrench on the assembly element to be tightened or loosened during a tightening or loosening rotational movement.
A further object of the invention is to provide a universal wrench which is easy to use and in particular allows polygonal elements located in inaccessible positions to be tightened or loosened.
The present invention thus concerns a universal wrench for tightening or loosening polygonal assembly elements, such as nuts, bolt heads or polygonal tube sleeves, this universal wrench including a wrench body provided with a handle and a wrench head arranged at one end of the handle and intended to come into contact with a polygonal assembly element to be tightened or loosened, the wrench head including a support body able to accommodate the polygonal assembly element, wherein the wrench further includes a flexible strap-shaped element intended to surround and hold the polygonal assembly element against the support body, one of the ends of the flexible strap-shaped element being fixed to the wrench head, and tension means associated with the handle and intended to act on the other end of the flexible strap-shaped element in order to place and hold the flexible strap-shaped element under tension, the wrench head being rotatably mounted with respect to the handle about a rotational axis parallel to the rotational axis of the polygonal assembly element to be tightened or loosened, so that a tightening or loosening rotational movement causes an increase in the tension of the flexible strap-shaped element thus assuring that the wrench is held gripped on the polygonal assembly element, and so that a so-called return rotational movement opposite to the tightening or loosening rotational movement causes the flexible strap-shaped element to relax thus allowing the wrench head to slide and grip another angle of the polygonal assembly element.
The solution provided by the present invention thus allows the assembly element to be gripped laterally like a wrench provided with adjustable jaws. The tightening and loosening torque is thus transmitted to the assembly element not by friction between the strap-shaped element and the object to be tightened or loosened as in strap or band wrenches of the prior art, but by a direct mechanical connection between the wrench head and the assembly element being gripped.
According to the present invention, because the wrench head is rotatably mounted with respect to the wrench handle so that a tightening or loosening rotational movement causes an increase in the tension of the flexible strap-shaped element and because an opposite rotational movement to the tightening or loosening rotational movement causes the flexible strap-shaped element to relax, it is not necessary to adjust the grip of the wrench on the assembly element since the latter is automatically disengaged during the opposite rotational movement to the tightening or loosening rotational movement in order to allow the latter to slide onto the polygonal assembly element and to grip another angle thereof. This is particularly advantageous in the event that the assembly element is located in an inaccessible position or if the rotational angle which it is possible to apply to the assembly element is limited.
It will be understood that, according to the present invention, the tightening rotational movement, the loosening rotational movement and the return rotational movement (that is a rotation movement opposite to a tightening or loosening rotational movement) depend on the position of the wrench with respect to the assembly element. It thus possible to apply a tightening rotational movement to the assembly element by disposing the wrench in a first position, and to apply a loosening rotational movement to the assembly element by disposing the wrench in a position opposite and symmetrical to the first position of the wrench. The return rotational movement is always defined as a rotational movement opposite to a tightening rotational movement, respectively to a loosening rotational movement, whether one wishes to tighten or respectively loosen the polygonal assembly element.
Advantageous embodiments of the present invention are the subject of dependent claims.
In particular, according to one embodiment of the invention, the wrench is preferably provided with return means linking the wrench head to the handle in an resilient manner in order to place the flexible strap-shaped element automatically under stress during an opposite rotational movement to the tightening or loosening rotational movement. Consequently, the wrench behaves like a ratchet handle, i.e. the wrench is held gripping the assembly element when the latter is subjected to a tightening or loosening rotational movement and can however slide or jump an angle of the polygonal assembly element when it is subjected to a rotational movement of relaxation or return rotational movement opposite to the tightening or loosening rotational movement, the wrench head again gripping another angle of the assembly element via the action of the return means, these means thereby placing the flexible strap-shaped element under tension.
Other advantageous embodiments will be presented in the following description.
Moreover, the flexible strap-shaped element can advantageously be made of a textile material, for example aramid fibres such as Kevlar (registered trademark).